Experimental methods and prospects on the measurement of electroweak $b$ and $c$-quark observables at the ILC operating at 250 GeV

International audienceThis paper describes a comprehensive experimental study on viability and prospects for the measurement of electroweak observables in $e^{+}e^{-}\rightarrow b\bar{b}$ and $e^{+}e^{-}\rightarrow c\bar{c}$ processes at the International Linear Collider (ILC) operating at 250 GeV of centre of mass energy. The ILC will produce electron and positron beams with different degrees of longitudinal polarisation (up to 80$\%$ for electrons and $30\%$ for positrons). The studies are based on a detailed simulation of the International Large Detector (ILD) concept. This will allow to inspect in detail the four independent chirality combinations of the electroweak couplings to electrons and other fermions and also perform background free analysis. The ILD design is based on the particle flow approach and the excellent vertexing and tracking capabilities, including charged hadron identification thanks to the $dE/dx$. We evaluate the main sources of experimental systematic uncertainties and identify the key design aspects of the accelerator and detector that are crucial to achieve the required per mil level accuracy that matches the expected statistical accuracy